The solutions usually employed for amplifying the power of a pulsed RF signal use for example:                common-base class-C bipolar transistors with DC voltage emitter supply,        common-source class-AB LDMOS transistors with DC drain supply and controlled drain current.        
The first solution offers simplicity of implementation and zero consumption in the absence of pulses. However, it has quite a low gain and a moderate efficiency, and also a distortion of the base of the pulse due to the prebias.
The second solution is more complex to implement, but offers a high gain and respects the integrity of the pulse. However, it has a residual consumption between pulses. Its gain varies with temperature. The efficiency of the stage is reduced by the unnecessary consumption due to the biasing of the transistor.
In IFF amplification, the gate supply voltage is adjusted for a given drain current (quiescent bias current).
This voltage is also present only during the transmission period in order to cancel out the drain current outside the transmission period.
Also known are systems for automatic control of the quiescent drain current an automatic bias system such as that described in the patent U.S. Pat. No. 6,573,796. However, this system can be used in pulse mode only if the resulting drain current pulses are filtered by the system for measuring the drain current.
The devices of the prior art have notably certain drawbacks.
For IFF (Identification Friend or Foe) amplification, there is residual consumption between pulses—the turn-on time of the transistor obtained with a pulsed gate voltage control is slow compared with the time to establish a square pulse (radar or IFF type). It is therefore essential to anticipate the control relative to the RF pulse to be amplified in order to avoid distorting it, thereby leaving a period over which the transistor consumes power.
As regards the automatic bias system, this cannot be used as it stands and has the drawback of having a residual consumption between pulses (quiescent current).
In general, the power consumption between pulses (increased heating, reduced efficiency) is greater the higher the maximum gain sought.
The amplification stage thus constituted does not contribute to reducing the residual radiation between pulses.